In CSS, what is the difference between static (default) positioning and relative positioning?
Relative position is relative to the normal flow. The relative position of that element (with offsets) is relative to the position where that element would have been normally if not moved.
You can see a simple overview here: W3School
Also, if I recall correctly, when declaring an element relative, it will by default stay in the same place as it otherwise should, but you gain the ability to absolutely position elements inside it relatively to this element, which I've found very useful in the past.